Branched polycarbonate resin and process for the preparation thereof

ABSTRACT

A branched polycarbonate resin which is prepared by using a tetrahydric phenol having a specific structure as the branching agent, has a branching agent content [branching agent/(dihydric phenol+terminating agent+branching agent)×100] of 0.05 to 0.5 mole % and satisfies the relationship: y≧11x +0.5 (wherein x is the branching agent content of the resin; and y is the melt tension (g) thereof at 280° C.); and a process for preparing a branched polycarbonate from a dihydric phenol, phosgene or a carbonic acid ester, a branching agent and an terminating agent, characterized by preparing an oligocarbonate, particularly one having chloroformate groups without the addition of the terminating agent, and then reacting the oligocarbonate with the dihydric phenol and the terminating agent. This process can provide a branched polycarbonate which is lowered in the branching agent content, exhibits a high melt tension and good melt characteristics, and can be stably molded through blow molding, extrusion, vacuum forming and so on.

TECHNICAL FIELD

The present invention relates to a branched polycarbonate resin and amethod for producing it, and precisely to a branched polycarbonate resinof which the branching agent content is low and the melt tension is highand which therefore has improved moldability in blow molding, extrusion,vacuum forming and so on, and also to a method for producing the resin.

BACKGROUND OF THE INVENTION

Generally having good transparency, good heat resistance and goodmechanical properties, polycarbonate resins to be produced frombisphenol A and others have many applications in various fields.However, the polycarbonate resins generally have low melt tension.Therefore, when molded through blow molding, extrusion, vacuum formingand so on, they are often defective in that their moldings could not allthe time have even thickness. In addition, as they often draw down whilebeing molded, they could not be formed into satisfactory moldings.

For overcoming the defects, Japanese Patent Laid-Open No. 47228/1984discloses a method of adding from 0.1 to 2.0 mol % or so of a branchingagent having three functional groups to a polymerization system to givea branched polycarbonate resin. The melt tension of the branchedpolycarbonate resin as produced according to that method could surely beincreased in some degree, but is not still on a satisfactory level. Onthe other hand, in order to produce a branched polycarbonate resinhaving a satisfactory level of melt tension according to the method, alarge amount of the branching agent must be used. In that case, however,increasing the amount of the branching agent added will lead to anunfavorable situation where crosslinked polycarbonate resins are readilyproduced. This is problematic in that the resins are often gelled. Inaddition, it is said that, with the increase in the branching agentadded, the impact resistance of the polycarbonates produced is to lower.For these reasons, the acceptable amount of the branching agent islimited, and it is desired to reduce as much as possible the amount ofthe branching agent to be added.

On the other hand, U.S. Pat. No. 4,415,725 discloses a branchedpolycarbonate resin for which a tetrahydric phenol is used as thebranching agent. However, the branched polycarbonate resin has low melttension, and its moldability in blow molding, extrusion, vacuum formingand so on is not still satisfactory.

The object of the present invention is to provide a branchedpolycarbonate resin of which the branching agent content is controlledlow and which has high melt tension and good melt characteristics andcan be stably produced and molded through blow molding, extrusion,vacuum forming and so on.

DISCLOSURE OF THE INVENTION

We, the present inventors have assiduously studied so as to attain theobject noted above, and, as a result, have found that theabove-mentioned object can be attained by a specific polymerizationmethod of producing a branched polycarbonate resin in which is used atetrahydric phenol having a specific structure as the branching agent.On the basis of this finding, we have completed the present invention.

Specifically, the invention is to provide a branched polycarbonate resinand a method for producing it, which are mentioned below.

(1) A branched polycarbonate resin for which is used a tetrahydricphenol having a structure of the following general formula and servingas a branching agent, and which has a branching agent contentx:(branching agent/(dihydric phenol+terminating agent+branchingagent)×100) x, of from 0.05 to 0.5 mol % and satisfies a relationship ofy≧11x+0.5 where x indicates the branching agent content of the resin andy indicates the melt tension (g) of the resin at 280° C.:

wherein A, R¹, R² and p are as follows:

A represents a single bond, an alkylene or alkylidene group having from1 to 20 carbon atoms, a polymethylene group having from 3 to 20 carbonatoms, a cycloalkylene or cycloalkylidene group having from 5 to 20carbon atoms, an arylene or arylalkylene group having from 6 to 20carbon atoms, —O—, —CO—, —S—, —SO—, or —SO₂—;

R¹ represents a hydrogen atom, an alkyl group having from 1 to 8 carbonatoms, an aryl group having from 6 to 20 carbon atoms, or an arylalkylgroup having from 7 to 20 carbon atoms;

R² represents a halogen atom, an alkyl group having from 1 to 8 carbonatoms, an aryl group having from 6 to 20 carbon atoms, or an arylalkylgroup having from 7 to 20 carbon atoms;

p represents an integer of from 0 to 4.

(2) A method for producing a branched polycarbonate resin of (1) from adihydric phenol, phosgene or a carbonate compound, a branching agent anda terminating agent, wherein an oligocarbonate is first prepared withoutadding the terminating agent thereto, and thereafter the resultingoligocarbonate is reacted with the dihydric phenol and the terminatingagent.

(3) A method for producing a branched polycarbonate resin of (1) from adihydric phenol, phosgene, a branching agent and a terminating agent,wherein an oligocarbonate having chloroformate groups is first preparedwithout adding the terminating agent thereto, and thereafter theresulting oligocarbonate is reacted with the dihydric phenol and theterminating agent.

BEST MODE FOR CARRYING OUT THE INVENTION

The invention is described in detail hereinunder.

1. Branched polycarbonate resin:

The branched polycarbonate resin of the invention is characterized bythe following characteristics:

(1) Characteristics:

{circle around (1)} Branching agent content:

The branching agent content of the resin indicates the mol % of thebranching agent in the resin, relative to the number of all mols of(dihydric phenol+terminating agent+branching agent) therein, and fallsbetween 0.05 and 0.5 mol %, but preferably between 0.07 and 0.45 mol %.If the content is smaller than 0.05 mol %, the melt tension of the resinwill be low, and blow molding of the resin will be difficult. If, on theother hand, the content is larger than 0.5 mol %, the resin will becrosslinked and gelled whereby the impact resistance of the moldings ofthe resin will be low.

{circle around (2)} Relationship between the branching agent content, x,and the melt tension, y (g), at 280° C.:

The resin must satisfy a relationship of y≧11x+0.5, preferablyy≧13x+0.5, more preferably y≧14x+0.5, where x indicates the branchingagent content of the resin and y indicates the melt tension of the resinat 280° C. The melt tension of the resin increases with the increase inthe amount of the branching agent added to the resin. However, thepolycarbonate resin will be crosslinked and gelled, if the amount of thebranching agent added thereto increases too much. Therefore, it isnecessary to control low the amount of the branching agent to be addedto the resin while realizing high melt tension of the resin.

{circle around (3)} Viscosity-average molecular weight (Mv):

Preferably, the viscosity-average molecular weight (Mv) of the resinfalls between 19000 and 37000, more preferably between 20000 and 30000.If Mv is smaller than 19000, the melt tension of the resin will be low,and blow molding of the resin will be difficult. If larger than 37000,however, the fluidity of the resin will be lowered and the moldabilitythereof will be poor.

(2) Method for production:

The method for producing the branched polycarbonate resin of theinvention is not specifically defined. Starting materials to bementioned hereinunder may be used for producing the resin. Concretely,for example, a dihydric phenol, phosgene or a carbonate compound, and aspecific branching agent are reacted optionally along with any othercomponents necessary for the reaction, but without adding a terminatingagent thereto, to prepare an oligocarbonate, and thereafter theresulting oligocarbonate is reacted with a dihydric phenol and aterminating agent. This is one preferred embodiment for producing theresin of the invention. In the step of adding the terminating agent tothe oligocarbonate in the embodiment, it is desirable that both thedihydric phenol and the terminating agent are not added at the same timeto the oligocarbonate, but the dihydric phenol only is first addedthereto so that it is reacted with the oligocarbonate, and thereafterthe terminating agent is added thereto.

(i) Starting materials:

The resin of the invention is produced from starting materials of adihydric phenol, phosgene or a carbonate compound, a branching agent anda terminating agent.

{circle around (1)} The dihydric phenol includes hydroquinone,4,4′-dihydroxydiphenyl, bis(4-hydroxyphenyl)alkanes,bis(4-hydroxyphenyl)cycloalkanes, bis(4-hydroxyphenyl)alkanes,bis(4-hydroxyphenyl)cycloalkanes, bis(4-hydroxyphenyl) oxide,bis(4-hydroxyphenyl) sulfide, bis(4-hydroxyphenyl) sulfone,bis(4-hydroxyphenyl) ketone, 9,9-bis(4-hydroxyphenyl)fluorene, etc., andtheir halogenated derivatives. Of those, preferred is2,2-bis(4-hydroxyphenyl)propane (bisphenol A). These dihydric phenolsmay be used either singly or as combined. Any other difunctionalcompounds (for example, dicarboxylic acids such as decanedicarboxylicacid, etc.) except dihydric phenols may also be used along with theabove-mentioned dihydric phenols.

{circle around (2)} The carbonate compound includes diaryl carbonatessuch as diphenyl carbonate, etc.; and dialkyl carbonates such asdimethyl carbonate, dimethyl carbonate, etc. These carbonate compoundsmay be used either singly or as combined.

{circle around (3)} The branching agent is represented by the followinggeneral formula:

wherein A, R¹, R² and p are as follows:

A represents a single bond, an alkylene or alkylidene group having from1 to 20 carbon atoms, a polymethylene group having from 3 to 20 carbonatoms, a cycloalkylene or cycloalkylidene group having from 5 to 20carbon atoms, an arylene or arylalkylene group having from 6 to 20carbon atoms, —O—, —CO—, —S—, —SO—, or —SO₂—;

R¹ represents a hydrogen atom, an alkyl group having from 1 to 8 carbonatoms, an aryl group having from 6 to 20 carbon atoms, or an arylalkylgroup having from 7 to 20 carbon atoms;

R² represents a halogen atom, an alkyl group having from 1 to 8 carbonatoms, an aryl group having from 6 to 20 carbon atoms, or an arylalkylgroup having from 7 to 20 carbon atoms;

p represents an integer of from 0 to 4.

Specific compounds for the branching agent are1,1,2,2-tetrakis(4-hydroxyphenyl)ethane,1,1,3,3-tetrakis(4-hydroxyphenyl)propane,2,2,5,5-tetrakis(4-hydroxyphenyl)hexane,2,2,4,4-tetrakis(4-hydroxyphenyl)pentane,1,1,2,2-tetrakis(3-methyl-4-hydroxyphenyl)ethane,2,2,6,6-tetrakis(3-methyl-4-hydroxyphenyl)octane,1,1,6,6-tetrakis(3-chloro-4-hydroxyphenyl)heptane,2,2,5,5-tetrakis(3,5-dimethyl-4-hydroxyphenyl)hexane,2,2,5,5-tetrakis(3-bromo-5-methyl-4-hydroxyphenyl)hexane,2-(2-hydroxyphenyl)-2,5,5-tris(4-hydroxyphenyl)hexane,2-(4-hydroxyphenyl)-2,5,5-tris(3-chloro-4-hydroxyphenyl)hexane,2-(3,5-dichloro-4-hydroxyphenyl)-2,5,5-tris(3-chloro-4-hydroxyphenyl)hexane,2-(3-chloro-2-hydroxyphenyl)-2,5,5-tris(3-chloro-4-hydroxyphenyl)hexane,2,2,5,5-tetrakis(3-tert-butyl-5-methyl-4-hydroxyphenyl)hexane,2,2-bis(4-hydroxyphenyl)-5,5-bis(3-methyl-4-hydroxyphenyl)hexane,α,α,α′,α′-tetrakis(4-hydroxyphenyl)-p-xylene,α,α,α′,α′-tetrakis(3-methyl-4-hydroxyphenyl)-p-xylene,α,α′-dimethyl-α,α,α′,α′-tetrakis(4-hydroxyphenyl)-p-xylene, etc. Ofthose, preferred is 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane.

These branching agents may be used either singly or as combined.

{circle around (4)} The terminating agent is not specifically definedfor its structure, provided that it is a monohydric phenol. For example,it includes p-tert-butylphenol, p-tert-octylphenol, p-cumylphenol,p-tert-amylphenol, p-nonylphenol, p-cresol, 2,4,6-tribromophenol,p-bromophenol, 4-hydroxybenzophenone, phenol, etc. These terminatingagents may be used either singly or as combined.

(ii) Various additives such as antioxidants, lubricants, anti-weatheringagents, colorants, nucleating agents and others may be added to theresin of the invention, so far as they do not interfere with thecharacteristics of the resin. Where the resin is used for sheets in thefield of construction materials, anti-weathering agents are preferablyadded thereto. For foamed sheets, nucleating agents are preferably addedto the resin.

2. Method for producing the branched polycarbonate resin mentionedabove:

It is desirable that the branched polycarbonate resin of the inventionis produced according to the method mentioned below.

Starting materials of a dihydric phenol, phosgene or a carbonatecompound but preferably phosgene, a branching agent and a terminatingagent such as those mentioned hereinabove are used to produce thebranched polycarbonate resin. First prepared is an oligocarbonate,preferably one having chloroformate groups. For this, it is desirablethat a dihydric phenol, phosgene or a carbonate compound but preferablyphosgene, a branching agent and any other optional components necessaryfor the reaction are reacted, without adding a terminating agentthereto, to give an oligocarbonate, preferably one having chloroformategroups. Next, the resulting oligocarbonate is reacted with a dihydricphenol and a terminating agent. If the starting materials of a dihydricphenol, phosgene or a carbonate compound, a branching agent and aterminating agent are put into a reactor all at the same time, andreacted in one step to give a polycarbonate resin, the melt tension ofthe resin produced will be low even though the molecular weight thereofcould be comparable to that of the resin as produced in the preferredmanner as above.

More preferably, in the step of adding the dihydric phenol and theterminating agent to the oligocarbonate, the terminating agent is notadded thereto simultaneously with the dihydric phenol, but the dihydricphenol only is first added thereto and reacted with the oligocarbonateand thereafter the terminating agent is added thereto. The growth of theoligocarbonate to be the intended polymer is terminated by adding theterminating agent to the growing oligocarbonate. Therefore, theoligocarbonate is first reacted with the dihydric phenol added theretoto thereby prolong the polymer chain to some degree, and thereafter theterminating agent is added thereto. According to this method, theshortest chains extending from the branching agent in the branchedpolycarbonate resin formed could be longer and therefore the melttension of the resin could be increased more, even though theviscosity-average molecular weight and the branching agent content ofthe resin are the same as those of the resin to be produced in differentmethods. On the other hand, however, if the terminating agent is addedto the oligocarbonate simultaneously with the dihydric phenol thereto,the chains from the branching agent in the oligocarbonate will firstreact with the terminating agent before they react with the dihydricphenol to be longer. If so, it is difficult to further prolong thechains from the branching agent in the oligocarbonate, and therefore themelt tension of the resulting resin could not increase even though theviscosity-average molecular weight and the branching agent content ofthe resin are comparable to those of the resin as produced in thepreferred manner as above. The time at which the terminating agent isadded to the oligocarbonate is described. Concretely, to theoligocarbonate having chloroformate groups, it is desirable that theterminating agent is added at the time at which the chloroformate groupsstill remain in the oligocarbonate in an amount equimolar to the amountof the terminating agent to be added to the oligocarbonate, or that is,the terminating agent shall be added thereto before all chloroformategroups in the oligocarbonate have reacted with the dihydric phenol addedthereto. In other words, it is desirable that the terminating agent isadded to the oligocarbonate at the time at which the amount of thechloroformate groups remaining in the oligocarbonate still fall between5 and 60 mol % relative to 100 mol % of the chloroformate groupsoriginally existing in the oligocarbonate before the dihydric alcohol isadded to the oligocarbonate.

(iii) Various additives such as antioxidants, lubricants,anti-weathering agents, colorants, nucleating agents and others may beadded to the resin of the invention, so far as they do not interferewith the characteristics of the resin. Where the resin is used forsheets in the field of construction materials, anti-weathering agentsare preferably added thereto. For foamed sheets, nucleating agents arepreferably added to the resin.

The invention is described in more detail with reference to thefollowing Examples, which, however, are not intended to restrict thescope of the invention.

In the following Examples and Comparative Examples, theviscosity-average molecular weight (Mv) and the branching agent contentof the resin samples produced were obtained according to the methodsmentioned below.

Mv:

Using an Ubbelohde's viscometer, the limiting viscosity [η] of a resinsample in a methylene chloride solution at 20° C. was measured, and theviscosity-average molecular weight, Mv, of the resin was obtainedaccording to the following relational formula:

[η]=1.23×10⁻⁵·Mv^(0.83)

Branching agent content:

Resin flakes were decomposed in an alkali, and the branching agentcontent of the resin was obtained through liquid chromatography.

Melt tension:

A resin sample was extruded out through an orifice with L/D=8/2.1, at atemperature of 280° C., at an extrusion rate of 10 mm/min, and at atake-up rate of 157 mm/sec, whereupon the tension (g) of the resin wasmeasured.

Example 1

Production of branched polycarbonate A:

0.043 mol of 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane (TEP-DF from AsahiChemical Material Industry), 9.2 mols of bisphenol A, 9.4 liters of anaqueous solution of 2.0 N sodium hydroxide, and 8 liters ofdichloromethane were put into a 50 liters container equipped with astirrer, and stirred therein, to which phosgene was introduced for 30minutes. Next, 0.44 mol of bisphenol A, 0.022 mol of triethylamine, and4.5 liters of an aqueous solution of 0.2 N sodium hydroxide were addedthereto, and reacted for 40 minutes, and thereafter the aqueous phaseand the organic phase in the reaction mixture were separated from eachother. Thus was prepared a dichloromethane solution of anoligocarbonate.

0.44 mol of p-tert-butylphenol was dissolved in the resultingoligocarbonate, to which was added a solution of 335 g of sodiumhydroxide and 2.2 mols of bisphenol A as dissolved in 4.5 liters ofwater. To this were further added 0.017 mols of triethylamine and 6liters of dichloromethane. These were stirred at 500 rpm and reacted for60 minutes. After the reaction, the aqueous phase and the organic phasein the reaction mixture were separated from each other. The organicphase was then washed with water, an alkali (aqueous solution of 0.03 Nsodium hydroxide), an acid (0.2 N hydrochloric acid) and again water inthat order (this was washed with water twice in total). After havingbeen thus washed, dichloromethane was removed from this. Thus wereobtained polycarbonate flakes, which were then dried at 120° C. for 24hours.

The polycarbonate obtained herein had a viscosity-average molecularweight of 30000, a branching agent content of 0.35 mol %, and a melttension of 8.9 g.

Comparative Example 1

Production of branched polycarbonate a:

The same process as in Example 1 was repeated, except that1,1,1-tris(4-hydroxyphenyl)ethane was used in place of1,1,2,2-tetrakis(4-hydroxyphenyl)ethane. The polycarbonate obtainedherein had a viscosity-average molecular weight of 25100, a branchingagent content of 0.35 mol %, and a melt tension of 3.0 g.

Example 2

Production of branched polycarbonate B:

The same process as in Example 1 was repeated, except that the amount of1,1,2,2-tetrakis(4-hydroxyphenyl)ethane which was 0.043 mol in Example 1was reduced to a half, 0.0215 mol, and that the amount ofp-tert-butylphenol which was 0.44 mol in Example 1 was changed to 0.40mol herein.

The polycarbonate obtained herein had a viscosity-average molecularweight of 27600, a branching agent content of 0.17 mol %, and a melttension of 3.2 g.

Comparative Example 2

Production of branched polycarbonate b:

The same process as in Example 2 was repeated, except that1,1,1-tris(4-hydroxyphenyl)ethane was used in place of 1,1,2,2-tetrakis(4-hydroxyphenyl) ethane. The polycarbonate obtained herein had aviscosity-average molecular weight of 22800, a branching agent contentof 0.17 mol %, and a melt tension of 0.7 g.

Comparative Example 3

Production of branched polycarbonate c:

0.018 mol of 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane (TEP-DF from AsahiChemical Material Industry), and 10 mols of bisphenol A were dissolvedin 10 liters of an aqueous solution of 2.0 N sodium hydroxide, in a 50liters container equipped with a stirrer. A solution of 0.37 mol ofp-tert-butylphenol as dissolved in 8 liters of dichloromethane, and 28ml of triethylamine were added thereto, and stirred at 300 rpm. To thiswas introduced phosgene at a flow rate of 30 g/min, for 47 minutes.After the reaction, the aqueous phase and the organic phase in thereaction mixture were separated from each other. The organic phase wasthen washed with water, an alkali (aqueous solution of 0.03 N sodiumhydroxide), an acid (0.2 N hydrochloric acid) and again water in thatorder (this was washed with water twice in total). After having beenthus washed, dichloromethane was removed from this. Thus were obtainedpolycarbonate flakes, which were then dried at 120° C. for 24 hours.

The polycarbonate obtained herein had a viscosity-average molecularweight of 27700, a branching agent content of 0.17 mol %, and a melttension of 2.1 g.

INDUSTRIAL APPLICABILITY

The branching agent content of the branched polycarbonate resin of theinvention is controlled low, and the melt tension of the resin is high.The resin has good melt characteristics and is suitable to applicationsfor blow molding, extrusion, vacuum forming and so on.

What is claimed is:
 1. A method for producing a branched polycarbonateresin comprising reacting with at least one compound selected from thegroup consisting of phosgene, dihydric phenol, and carbonate with abranching agent to produce an oligocarbonate; and reacting saidoligocarbonate with dihydric phenol and a terminating agent.
 2. Themethod of claim 1, wherein said branched polycarbonate resin has abranching agent content x, wherein x equals branching agent/(dihydricphenol+terminating agent+branching aget)×100, and wherein x is from 0.05to 0.5 mol % and the resin satisfies the relationship of y≧11x+0.5,wherein y represents the melt tension (g) of the resin at 280° C.
 3. Themethod of claim 2, wherein the resin satisfies the relationship ofy≧13x+0.5.
 4. The method of claim 2, wherein the resin satisfies therelationship of y≧14x+0.5.
 5. The method of claim 1, wherein theviscosity-average molecular weight of the branched polycarbonate resinis from 19000 and
 37000. 6. The method of claim 1, wherein saidoligocarbonate is reacted with dihydric phenol followed by saidterminating agent.
 7. The method of claim 1, wherein the dihydric phenolis selected from the group consisting of hydroquinone,4,4′-dihydroxydiphenyl, bis(4-hydroxyphenyl)alkanes,bis(4-hydroxyhenyl)cycloalkanes, bis(4-hydroxyphenyl)alkanes,bis(4-hydroxyphenyl)cycloalkanes, bis(4-hydroxyphenyl)oxide,bis(4-hydroxyphenyl) sulfide, bis(4-hydroxyphenyl) sulfone,bis(4-hydroxyphenyl) ketone, 9,9-bis(4-hydroxyphenyl)fluorene, andmixtures thereof.
 8. The method of claim 1, wherein said carbonate is adiaryl carbonate or a dialkyl carbonate.
 9. The method of claim 1,wherein said branching agent of the formula:

wherein A, R¹, R² and p are as follows: A represents a single bond, analkylene or alkylidene group having from 1 to 20 carbon atoms, apolymethylene group having from 3 to 20 carbon atoms, a cycloalkylenehaving from 5 to 20 carbon atoms, a cycloalkylidene group having from 5to 20 carbon atoms, an arylene having from 6 to 20 carbon atoms, anarylalkylene group having from 6 to 20 carbon atoms, —O—, —CO—, —S—,—SO—, or —SO₂—; R¹ represents a hydrogen atom, an alkyl group havingfrom 1 to 8 carbon atoms, an aryl group having from 6 to 20 carbonatoms, or an arylalkyl group having from 7 to 20 carbon atoms; R²represents a halogen atom, an alkyl group having from 1 to 8 carbonatoms, an aryl group having from 6 to 20 carbon atoms, or an arylalkylgroup having from 7 to 20 carbon atoms; p represents an integer of from0 to
 4. 10. The method of claim 1, wherein said terminating agent is amonohydric phenol.